Re: [PATCH 02/17] block: add a bdev_rw_virt helper

Hannes Reinecke
2025-04-23T06:07:22Z

On 4/22/25 16:26, Christoph Hellwig wrote:
> Add a helper to perform synchronous I/O on a kernel direct map range.
> Currently this is implemented in various places in usually not very
> efficient ways, so provide a generic helper instead.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> block/bio.c | 30 ++++++++++++++++++++++++++++++
> include/linux/bio.h | 5 ++++-
> 2 files changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 4e6c85a33d74..a6a867a432cf 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1301,6 +1301,36 @@ int submit_bio_wait(struct bio *bio)
> }
> EXPORT_SYMBOL(submit_bio_wait);
>
> +/**
> + * bdev_rw_virt - synchronously read into / write from kernel mapping
> + * @bdev: block device to access
> + * @sector: sector to accasse
> + * @data: data to read/write
> + * @len: length to read/write
> + * @op: operation (e.g. REQ_OP_READ/REQ_OP_WRITE)
> + *
> + * Performs synchronous I/O to @bdev for @data/@len. @data must be in
> + * the kernel direct mapping and not a vmalloc address.
> + */
> +int bdev_rw_virt(struct block_device *bdev, sector_t sector, void *data,
> + size_t len, enum req_op op)
> +{
> + struct bio_vec bv;
> + struct bio bio;
> + int error;
> +
> + if (WARN_ON_ONCE(is_vmalloc_addr(data)))
> + return -EIO;
> +
> + bio_init(&bio, bdev, &bv, 1, op);
> + bio.bi_iter.bi_sector = sector;
> + bio_add_virt_nofail(&bio, data, len);
> + error = submit_bio_wait(&bio);
> + bio_uninit(&bio);
> + return error;
> +}
> +EXPORT_SYMBOL_GPL(bdev_rw_virt);
> +
> static void bio_wait_end_io(struct bio *bio)
> {
> complete(bio->bi_private);
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 0678b67162ee..17a10220c57d 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -402,7 +402,6 @@ static inline int bio_iov_vecs_to_alloc(struct iov_iter *iter, int max_segs)
>
> struct request_queue;
>
> -extern int submit_bio_wait(struct bio *bio);
> void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table,
> unsigned short max_vecs, blk_opf_t opf);
> extern void bio_uninit(struct bio *);
> @@ -434,6 +433,10 @@ static inline void bio_add_virt_nofail(struct bio *bio, void *vaddr,
> __bio_add_page(bio, virt_to_page(vaddr), len, offset_in_page(vaddr));
> }
>
> +int submit_bio_wait(struct bio *bio);
> +int bdev_rw_virt(struct block_device *bdev, sector_t sector, void *data,
> + size_t len, enum req_op op);
> +
> int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
> void bio_iov_bvec_set(struct bio *bio, const struct iov_iter *iter);
> void __bio_release_pages(struct bio *bio, bool mark_dirty);

Any specific reason why the declaration of 'submit_bio_wait()' is moved?

Other than that:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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